1. Field of the Invention
The present invention relates to a production planning apparatus and method for an industrial product and in particular to a production planning apparatus and method for a product to be produced through multiple steps in different production forms.
2. Description of the Related Art
Many companies in manufacture industries may perform a task called “Available to Promise” of, to a request from a sales department or a product dealer, that is, a request for “how many of which product by when”, checking whether the product can be manufactured and delivered as requested or not and answering “how many (amount) of which product are available by when (delivery time)”. The product subject to the Available to Promise, the delivery time and amount are informed to a production factory of the product of a manufacture company, and the production factory produces and ships the product so as to keep the delivery time and amount. A company not performing Available to Promise produces and ships a product in response to and accordance with a request from a sales department or dealer thereof.
In order to perform Available to Promise, attentions must be paid to following points. First of all, since the market competition is heating up in recent years, an order might highly possibly go to a different company when the Available to Promise takes time. Also, when a product could not be supplied by the promised delivery time, the reliability may be lowered, and subsequent orders may go to other companies.
Many technologies have been proposed for calculating the delivery time in consideration of production constraints by using a production planning apparatus in order to avoid these risks and perform secure Available to Promise. JP-A-2000-353190, for example, discloses an example thereof.
Though various production planning algorithms have been proposed which are executed in a planning portion of a production planning apparatus, all of the conventional technologies use a single algorithm to plan all production steps. JP-A-2001-34321 discloses a production planning apparatus as a technology in consideration of differences among multiple production steps included in production steps of a product. The production planning apparatus proposes an algorithm allowing the load leveling in packets in both of production assembly step and source step, which is a bottleneck, but adopts a common algorithm in the both steps.
Banbara et al, “Java Niyoru Isyu Kyocho Seiyaku Kaisyo System No Kaihatsu (Development of Heterogeneous Constraint Solving System)”, Information-technology Promotion Agency, FY2002, Project Reports Rev. 2 introduces a technology relating to use of multiple algorithms. The technology does not embody the production planning algorithm but is implemented for obtaining a larger advantage than that of tuning of a single algorithm by operating multiple heterogeneous constraint solvers (algorithms) cooperatively and competitively in parallel. The cooperative constraint solving system disclosed in the document includes different kinds of solvers and a scheduler portion for managing the solvers, and the scheduler portion causes the constraints solvers to cooperate/compete to manage so as to obtain a solution efficiently.
In order to produce one product, many companies distribute tasks to multiple sections including a section for processing parts and a section for producing a product by assembling processed parts. In order to supply a product quickly in accordance with a change in demand, such companies mainly have a supply chain among the sections so that items and information can be synchronized among the sections to produce the product. The supply chain was once provided among sections in one company but, in recent years, tends to be provided among multiple companies. For example, a company that manufactures/sells personal computers only informed an amount of supply based on the production plan of a factory of the company to a company that manufactures parts of personal computers, which are in an upstream task, (which will be called supplier, hereinafter). However, in recent year, the company that manufactures/sells personal computers increasingly devises a production plan for the personal computers by checking even the capacity of supply of the factory of the supplier. The production planning by checking even the capacity of supply of the supplier is made for minimizing the risk that a promised amount of supply is not supplied from the supplier and/or the risk due to the excessive parts inventory for securely producing and supplying products to the market, which were problems not addressed before.
A production plan must be devised or changed quickly in order to control the supply of products quickly in accordance with a change in demand. As one device for implementing the control, an information system may be adopted which devises production plans for factories of all sections sharing the tasks for producing products.
However, the production forms to be implemented by the factories do not always agree. The production forms may be divided into those of the process type and those of the assembly type, which have different constraint conditions on which the precision of the production plan depends. The assembly type has many parts to assemble, and whether required parts can be procured or not is an important issue for the production plan. An assembly task can be performed at a constant number of man-hours as far as required parts are available. On the other hand, since the process type has constraints of efficiency and/or yield of production tasks due to changes of the types of manufacture apparatus, the order of tasks is an important issue for the production plan. The above-described example relating to personal computers has a hard disk and memory module requiring the process type production step relating to semiconductor in the parts processing in the upstream of the production while requiring the assembly type manufacture step of assembling parts in the downstream step. Generally, many steps in upper streams of production may have process type production forms.
Material Requirements Planning (MRP) calculation method is an algorithm superior in production planning having parts as a constraint like the assembly type. MRP is a method for calculating a required amount of parts to order by exploding the product to be produced into parts, calculating a total amount of the parts required for the production and subtracting the inventory and stock on order therefrom. In other words, MRP calculation calculates a plan for procuring or manufacturing “a required amount (required amount) of required item (item) by a required time (delivery time)” for an item such as a part and a raw material based on a devised production level shipping plan thereof. MRP calculation does not calculate an order of tasks since the task times in steps are regarded as fixed values therein. For example, in order to produce products A and B by March 31, the result that the products A and B are to be charged on March 30 and the production will be completed on March 31 can be calculated if one day is required for producing the products. However, MRP calculation does not calculate which of the products A and B must be produced first.
On the other hand, a scheduling calculation method is an algorithm superior in production planning having an order of tasks as a constraint like the process type. Scheduling is a method for obtaining an order of tasks (in which order products must be produced) by handling the step operation times and product delivery time as constraints when multiple products must be produced in a step. In the production especially in multiple steps, the inter-step inventory of parts required for the production is not considered even if any.
Since algorithms suitable for devising a production plan depend on characteristics of steps in this way, a production planning apparatus adopting a single algorithm as described above cannot devise a production plan involving both assembly type and process type steps in consideration of constraint conditions of both of them simultaneously. If MRP is applied to the process type, the order of tasks cannot be considered. On the other hand, if the scheduling calculation method is applied to the assembly type, the inventory of parts and stock on order cannot be considered. A single algorithm may be developed which include both functions of MRP and scheduling and can devise a production plan in consideration of orders of assembly type and process type tasks and inventories. However, the calculation is excessive in quality and disadvantageously increases the calculation time.